Chevy & GMC Vans

So ya I know it doesn’t look like much....
What you’re looking at is a couple of years worth of scrounging and conniving to try to put together the closest thing to an unstoppable Safari as I could manage.
As it sits in the parking lot of Ct Axle and Mr. Peter Haney gets ready to roll it onto a lift to upgrade the front and rear differentials.
The rear is going to be receiving a new Detroit Truetrac Torsen style LSD carrier along with a complete rebuild of the 7.625” rear housing.
The cast iron 7.25” unit in the pic will be receiving at long last the MFactory Torsen style LSD carrier and a full master kit rebuild.

CooOOOoool.

Awesome!

Ok so here’s the first update. It took Ct. Axle one evening to install the Truetrac, re-shim/re-seal and re- bearing the rear, install the MFactory Torsen, re-shim/re-seal And re-bearing the spare front diff. Gotta love people who do the tricky stuff for a living.
Took it for a test drive. Pulled over on the side of the road. The shoulder was long grass and cambered away from the pavement so the entire van was listing heavily to starboard. That’s to the right for you landlubbers. Stomped it to he floor from a complete stop and the van shot straight ahead no attempt to follow the tug of gravity into the adjoining field. Minor steering input and we were back on pavement- very nondramatic. Next I found a level patch of dirt/stone and redid the above test. The van leapt forward with so little wheel spin I hardly left a mark.
So the traction is impressive. Not really any more so than the second handTorsen it replaced but now I KNOW the rear is set up right.
One reason for all this being done was a strange “ play” that develops in the driveline as it gets warm. There was internal play it my eBay Torsen so I figured “ mistakenly” that was what I was feeling. The play returned on the drive home so next step now that I have a pro built rear is to move forward to the Frankencase 236 transfer case. As some might recall back when I was researching the 136/236 comparability, I built a 236 out of junked 136 and 236 units. Finding everything swappable was one of the steps towards “ yes it’ll fit/work”
I still have my stock 136 sitting on the shed floor so I’m gonna stick that back in for a day and see if the play goes away.
I have ordered two reconditioned cv axle units from Detroit Axle. I have one aftermarket and one stock with a torn boot to replace when the cast iron LSD’d front diff gets swapped in sometime this month.
So that’s it for today. I’ll get back with an update after my day of stressing my drivetrain with the 136 back under the van

Ct. got its first snow this weekend and I got a chance to see what it’s like to drive an AWD Safari with twin Torsen’s in the snow. The first word that comes to mind is BORING!
So let’s go back to when the van was stock with open diffs front and rear. Open diffs put power to the wheel with the least amount of traction. Step on the gas in the snow and one wheel in the front and one wheel in the back would propel you forward in a nice straight line. Turning is a different set on circumstances however. Turn the wheel and step on the gas and the diffs once again put power to the wheel with the least amount of traction. That would be the wheel on the inside of the turn as weight is shifted to the outside in the turn. So the inside wheel with its reduced load spins and the outside wheel with no power slides sideways in a push. So you turn the wheel and nothing happens, you keep going straight.
So I put a torsen in the rear of the van. Now it brings me back to my old muscle car days with big blocks and posi rear ends. Stomp on the gas and be ready because the rear end is gonna try and pass you and will if you’re not paying attention. Sometimes it would even if you WERE paying attention! The added traction of the Torsen LSD really increased the rate of acceleration but you had to pay attention. The van was no longer idiot proof in a straight line.
Now introduce the front Torsen and its the complete package. The Torsen’s sense traction and dispense torque accordingly. Stomp on the gas on a snow covered road and with power to all four wheels and the units constantly adjusting torque distribution, you are accelerating effortlessly in a straight line.
Now let’s go around a corner...In the snow. This l is where Torsen’s truly shine! Power is fed to the wheels with the most traction. The loaded outside wheel has the most power. Turn the wheel and the van goes around the corner. There is some added benefit I believe to running this setup with the 136/236/246 transfer case. As the front shaft is always turning due to clutchpack preload there is always torque being applied to the front diff. Not much but some. This seems to give you a bit of a “ head start” when cornering in the snow. The rear doesn’t try to push you straight thru the corner like a locker or even a clutch style LSD. The front, being powered at all times simply goes where it’s pointed. Braking early and getting back on the gas in the turn has always been the proper way to drive and with this setup-in the snow-it’s just awe inspiring.
There is one more advantage to the Torsen diff. And that is during braking. Torque sensing doesn’t happen just during acceleration. These units continue to perform their torque distribution role as long as you are rolling. It is very hard to upset this vehicle. It just goes where you point it.
I will continue to look for ways to test this setup and report back. Right now it’s all smiles.

You know captn.crunch you are ruining my life! Here I was all happy with my 236 t.case thinking I really don’t “wheel” too much so I don’t need that dif he is talking about.... then comes this post. You say snow and I am listening.... I waited on 4wd till I could retain AWD for this very reason.

Subscribed.....

Ryan

Hey Ryan
Ya I’m sorry about all of this. I don’t know what came over me. I could have gone thru life content with the more than capable stock AWD Safari. But nooooooooo! I HAD to see if the 236 would work. I HAD to have twin Torsen’s. And now look what I’ve done. There’s people all around the world hitting themselves in the head saying “ I coulda had a 236.” I must admit to a bit of a perverse pleasure in seeing np236 in peoples signature though. It is an awesome mod that has no detractors and that’s the point of making improvements. Having them actually be improvements and not a compromise on what you already had.
Now it’s the twin Torsen upgrade. I still have more testing to do under more conditions but all I can say right now is WOW! It’s like a different van. Night and day-black and white-apples and oranges. No comparison. I really think the clutch preload is a plus with this. I would love to be able to drive a Torsened 231 swap to compare or an Engineered Performance equipped to test against but I’ll continue to push mine to see what it’ll do and report back.
Thanks for following along and for believing enough in what I’ve come up with to incorporate it into a vehicle you climb into and set off for parts unknown in

Captn. Crunch wrote:
There is one more advantage to the Torsen diff. And that is during braking. Torque sensing doesn’t happen just during acceleration. These units continue to perform their torque distribution role as long as you are rolling. It is very hard to upset this vehicle.
.

I'm sorry but this should read engine braking. Taking your foot off the gas and/or downshifting will introduce "negative torque" for lack of a real term. The differentials will continue to function . Once you take your foot off the gas and step on the brake pedal and remove all driveline tension, the diffs will act as an open diff.

So I wanted to understand this diff more and found this video depicting how these things work.

https://m.youtube.com/watch?v=JEiSTzK-A2A

Pretty stinking cool.

Ryan

Snowgeek wrote:So I wanted to understand this diff more and found this video depicting how these things work.

https://m.youtube.com/watch?v=JEiSTzK-A2A

Pretty stinking cool.

Ryan

Torsen tech. is very cool. I fell in love with the mathematics and the physics involved in the design. I love how the design “senses” traction differences. I love how it’s seemless and has no parts to wear out. By the way I love these things.
I really took a gamble on the twin Torsen thing. There were only a few instances of this being done throughout the entire automotive world and they were big dollar German engineeredAudi types. I’m just a little nervous as I sing the twin Torsen praise tune though. People have followed me down the np236 path and it seems to be on its way to becoming THE swap of choice and for good reason. The 236 is an easy inexpensive swap and the wiring tutorial has been streamlined nicely. This iron diff/front Torsen is a whole nother ball of wax. This is not a cheap and easy mod and it affects the very soul of your vehicle, how it translates road feel to the driver. I’ve named my van the mule. Short for test mule and that’s just what she is. I’ve torn her apart and slammed her back together so many times with so many different combinations of parts that there has to be an identity crisis of some kind going on. I never really finish anything either. Once I know it fits or works that’s good enough so ya she’s very rough. I’m so used to how it handles and I’m so far removed from stock that I’m quite immune to creaks and groans and hops and all the things that go with running a modified experimental IFS. I also believe this will be my last round of mods for the old girl. Im going to spend a little time tightening things up and just drive. All of this work dedicated to max traction cries out for some off-roading so I’ll spend some time on the trails and see how we stack up against Tacoma’s and fj’s.
Im worried someone’s going to go thru a lot of money time and effort and not like the results. This is such a subjective thing-vehicle balance and front end feedback. There’s no denying what incredible balance twin Torsen’s bring to driving in the snow. It has to be experienced to be believed its that profound. So here’s to keeping my evaluations factual, here’s to anyone following my lead making sure they are mechanically sound as I take no responsibility for folks inability to adapt to changes incurred after modifications are accrued.
Here’s to those of you out there with vans in much better shape than my poor mule who will undertake these mods and go the extra mile, spend the extra dollar and invest the extra hour to bring out the absolute best these upgrades can bring to our vans.
I have literally spent years researching on line the possibilities of success with these mods.

https://www.zr2usa.com/mboard/index.php ... 36/&page=2

Here is a link to how far down the rabbit hole I went with the Zr2 guys. I believe that thread dates back to 06/14 so ya three + years worth of hypothetical dialog.
Thank you for trusting in my work, the theories behind my work and thank you especially for trusting in all of this enough to not only invest your time and money but to do so in vehicles that carry you and your loved ones over the river and thru the woods!

Captn. Crunch wrote:Torsen tech. is very cool. I fell in love with the mathematics and the physics involved in the design. I love how the design “senses” traction differences. I love how it’s seemless and has no parts to wear out. By the way I love these things.
I really took a gamble on the twin Torsen thing. There were only a few instances of this being done throughout the entire automotive world and they were big dollar German engineeredAudi types.

Don't forget about the Humvee(HMMWV), few hundred thousand of them.

True True